Antennas which are used to transmit and receive radio waves have been widely applied in systems such as telecommunications, Wireless Local Area Networks (WLANs), television broadcasting and radars, etc. Since a single antenna has many limits, for example it provides a low value of directivity, antenna arrays which each consists of more than one single antenna, i.e. antenna element, have been developed.
In an antenna array, by combining antenna elements in such a way that signals at particular angles experience constructive interference while others experience destructive interference, beamforming technique can achieve good spatial selectivity, and thus has been rapidly developed in rent decades.
In order to implement beamforming, many methods, such as Convex Optimization, Orthogonal Method and metaheuristic methods, have been proposed. Among these beamforming methods, Convex Optimization can realize an optimism object of maximizing sidelobe attenuation and minimizing mainlobe ripple, but cannot be applied to realize an optimism object of matching a given beam pattern. In contrast, Orthogonal Method can be used to realize the beam pattern matching problem in some cases, for example in case that the object beam pattern can be perfectly reached. But if the object beam pattern cannot be exactly reached, for example, it is just an object which can be approached rather than being reached, or if the optimism object is to maximizing sidelobe attenuation and minimizing mainlobe ripple, Orthogonal Method is unable to provide a satisfactory result. That is, none of Convex Optimization and Orthogonal Method has a wide range of use.
As another kind of beamforming methods, metaheuristic methods include Genetic Algorithms (GA), Differential Evolution Algorithm (DEA), and Particle Swarm Optimization (PSO) and so on. Although metaheuristic methods can realize both of the above-mentioned optimism objects and thus have a wide range of use, they have a very low computing speed, which makes them not practical in the field of antenna arrays.
Accordingly, there is a need to develop a beamforming method and a beamforming apparatus which not only have a wide range of use but also have a fast computing speed.